Evolution 01.22.08 / 01.23.08. What if I don’t believe it? Consider Acts 17:22-23 –Paul then stood up in the meeting of the Areopagus and said: "Men of.

Evolution

01.22.08 / 01.23.08

What if I don’t believe it?

• Consider Acts 17:22-23– Paul then stood up in the meeting of the

Areopagus and said: "Men of Athens! I see that in every way you are very religious. For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: TO AN UNKNOWN GOD. Now what you worship as something unknown I am going to proclaim to you.

What if I don’t believe it?

• Ask yourself if you even understand it?

• Realize that you really do believe it…

at least, some of it.– Evolution is a theory, which means it’s

complex– Parts of evolution are fact that no one

contests

So, why should I care?

• Do you know why purebred dogs are more likely to have health problems than mutts?

• Do you know why 1.7 million Americans now contract “superbug” infections each year?

• Pay attention and maybe you’ll find out even more.

So, why should I care?

• It’s everywhere

Chapter 14History of Life

01.22.08 / 01.23.08

Biogenesis

• Biogenesis – all living things comes from other living things– From Greek bioun meaning “life” and gignesthai meaning “beginning”

– Like the book of Genesis (the beginning)

• Spontaneous generation – the now abandoned view that life spontaneously arises– used to explain why maggots appeared on

rotting meat

Biogenesis

• Redi’s experiment (1600s)– observed that maggots turned into flies and

that maggots often seemed to appear after flies had been in the area

– experimental group had meat covered with netting to keep flies out

– control group had meat exposed to flies– demonstrated that maggots are produced

from living flies

Biogenesis

• Redi’s experiment– Hypothesis: maggots develop from flies– Independent variable: exposure to flies– Dependent variable: development of maggots– Data: observed maggots (yes or no)– Conclusion: maggots form from flies, not

spontaneously

Biogenesis

• Spallanzani’s experiment (1700s)– Tested the idea of a “vital

force”– Boiled broth to kill

microorganisms• Sealed flask of exp. group• Left control flask open

– Critics said the heat killed the “vital force”

Biogenesis

• Pasteur’s experiment (1800s)– used a curved, but open, neck on a flask to

keep microorganisms out of broth• broth remained clean for up to a year• once the neck was broken, broth was

contaminated within a day

Cell Theory

• These experiments led to Cell Theory, which states:– All living organisms are made of one or more cells– Cells are the basic unit of structure and function in all

living organisms– All cells come from other cells

• In general, evolutionary theory makes no effort to explain how life began, just how it has changed

Earth’s History

• The earth is about 4.6 billion years old

• Age is determined by radiometric dating– radioactive materials decay from their parent

isotopes into daughter isotopes– this decay occurs at a specific rate, known as

half-life

Earth’s History

• So, how did life begin?– Oparin and Haldane proposed in the 1920s

that the earth’s early atmosphere contained large amounts of ammonia, hydrogen gas, water vapor and methane

– These chemicals might have collected in water and, with the energy of lightning and solar radiation, combined into macromolecules, such as amino acids

Earth’s History

• Miller-Urey experiment– Tested Oparin and

Haldane’s hypothesis by combining inorganic chemicals with electricity

– Created organic materials, such as amino acids

– Various revisions have been made to test differing hypotheses for the early atmosphere

Earth’s History

• But, didn’t I say evolution does not try to explain how life began?– Yes– Miller received his PhD in chemistry, not

biology– But, science is interdisciplinary, so I said, “in

general.”• In general, evolutionary theory makes no effort to explain

how life began, just how it has changed

Earth’s History

• That leads us to astrobiology– Formerly known as exobiology– Study of life in the universe– Organic molecules have been found in

meteorites

Earth’s History

• Experiments have shown some organic molecules can form spontaneously– Microspheres are made of proteins that form a

membrane• a certain type of radioactive microsphere is now

used in oncology

– Coacervates are made of various molecules, including fats, amino acids and sugars

The First Life-Forms

• Read if you want to know more….

Check-up

• Describe the difference between spontaneous generation and biogenesis.

• Describe Redi’s experiment.

• Describe Spallanzani’s experiment.

• Describe Pasteur’s experiment.

Check-up

• How do you personally benefit from the research of Spallanzani and Pasteur?

• Describe cell theory.

• Describe the Miller-Urey experiment and its importance.